32 BRITISH ANNELIDS. 



Until last year the story of the Square-tail had never been fully 

 told by any English author. I had the honour, however, of giving a 

 lengthy sketch of its history in "Science Gossip," 1891, p. 80, and 

 must refer the reader to that periodical for illustrations and details. 

 When I speak of Allurus as the Square-tail, I wish it to be under- 

 stood that the term is to be used in a modified sense, as we have 

 one or two other worms which sometimes present this peculiarity, 

 only in a less marked degree. I am anxious, however, as far as 

 possible to attach to each species of worm a popular name which 

 will pretty accurately set forth its characteristic feature, so that it 

 may be possible to speak of each worm without being compelled 

 always to adopt the technical name of the species. Now it was on 

 account of the shape of the posterior half of this worm that it was 

 named Allurus (Greek alios, another, different, and ojira, tail or 

 hinderpart), when it was separated from the old genus Lumbricus, 

 and made the type of a new species. 



Savigny is the first author who gives us any information respect- 

 ing Allurus, which he named Enterion tetraedrum. This was in 

 1828, in which year Duges also wrote about it, and named it Amphis- 

 baena, because, like the serpent of which Lucanus sang, it could go 

 backwards as readily as forwards. In 1837, Duges regarded the two 

 worms as distinct, and called Savigny's species Lumbricus ietraedrus, 

 and his own Lumbricus amphisbcBna. The distinctions which he 

 points out have been overlooked by later writers until Eisen took up 

 the subject, and now we find two or three well-marked varieties whose 

 further study is likely to yield some interesting results. 



In 1843 Hoffmeister gave our worm a new name, calling it the 

 Agile-worm {Lumbricus agilis) ; but though the distinction is a good 

 one when the square tail and the green worm, for example, are con- 

 trasted, it does not hold good when the purple worm {Lumbricus 

 purpureus) and some others are placed in competition with it. Eisen 

 was the first to recognise its generic distinctness from Lumbricus, 

 and in 1870 gave it the name which it still continues to bear. Now 

 that it has come of age, and had its biography written, I hope no one 

 will venture to alter its name, and so add to the confusing list of 

 synonyms by which it is already obscured. 



Allurus ranges from one to two inches in length, but I have taken 

 it frequently in its adult stage under an inch long. It is the smallest 

 species we possess, and may easily be overlooked, not only by reason 

 of its diminutive size, but also on account of its protective coloura- 



